Diesel soot particulate filters comprising fibers such as metal or ceramic fibers are well known.
JP2002058939 describes a diesel soot filter, which comprises a construction of porous materials, for which the meshes of the filter have been made finer in the direction of the flow of the exhaust gas to be filtered.
The filter either comprises several filter medium layers, one adjacent to the other, for which each layer has a defined mesh coarseness, or as an alternative the mesh coarseness changes gradually over the depth of the filter medium.